With the rapid development of digital mobile multimedia broadcasting technology (e.g., mobile TV technology), mobile multimedia broadcasting terminal users are provided with a lot of services, such as advertisement, weather forecast, news, sports, variety, multimedia radio play, movie and other programs. The users can select service programs of mobile multimedia broadcasting according to their own hobbies.
A data card is a data service device used on a computer. The users can use mobile data services and receive multimedia messages through the data card. Moreover, multimedia play can be realized by adding a broadcast signal receiving chip on the data card. In addition, multiple functions, such as surfing the Internet and storing, can be integrated and extended on the data card.
In order to realize paid services and personalized services of a mobile multimedia broadcasting system, it is required to scramble program streams, and only authorized users can watch the programs. After being authorized, the users receive scrambled program streams, and descramble the program streams, and then programs can be played. At present, when receiving the scrambled program streams through the data card, the following two solutions are mainly adopted, and the two solutions are described below with reference to FIG. 1 and FIG. 2.
Solution 1: a system architecture as shown in FIG. 1 is composed of a data card and an Application Processor (AP), wherein the data card mainly comprises a receiving and demodulating chip, a descrambling module, a demultiplexing module and a Conditional Access System (CAS); the AP can be a terminal, such as a personal computer, a Personal Digital Assistant (PDA) and a netbook, and the AP comprises a player module. As shown in FIG. 1, the specific implementation is that: the receiving and demodulating chip is responsible for receiving and demodulating a digital broadcasting signal, namely the scrambled program stream, to obtain a data frame, and sends the data frame to the demultiplexing module; then, the demultiplexing module performs demultiplexing to the data frame to obtain a scrambled media data block and Entitlement Control Message (ECM), sends the obtained ECM to the CAS, and sends the scrambled media data block to the descrambling module; an Entitlement Management Message (EMM) is sent to the CAS through the transmission of a broadcast channel or an interactive channel (FIG. 1 shows the transmission through the interactive channel), and then, the CAS calculates a Control Word (CW) according to the EMM and the ECM, and then sends the CW to the descrambling module; the descrambling module uses the CW to descramble the scrambled media data block to obtain a clear stream, and sends the clear stream to the AP through a USB port; the AP decodes and plays the clear stream, wherein the transport protocol of the clear stream from the data card to the AP can adopt a non-secure transport protocol, for example, a common USB transport protocol (e.g., a common USB2.0).
It can be seen that in the above processing, for the security of keys, although the descrambling process is performed at the data card side, because the transport protocol of the clear stream from the data card to the AP adopts the common USB transport protocol, media contents transmitted based on the protocol cannot be protected; if there is a third party performing operations of monitoring, copying and the like to the USB port at this point, then media contents will be illegally copied and propagated.
Solution 2: a system architecture shown in FIG. 2 is still composed of a data card and an AP, but the descrambling module is set at the AP side, then the data card mainly comprises the receiving and demodulating chip, the demultiplexing module and the CAS, and the AP mainly comprises the descrambling module and the playing module. In this case, the specific implementation is that: the receiving and demodulating chip is responsible for receiving and demodulating the digital broadcasting signal to obtain the data frame, and sends the data frame to the demultiplexing module; then, the demultiplexing module performs demultiplexing to the data frame to obtain the scrambled media data block and the ECM, sends the obtained ECM to the CAS, and sends the scrambled media data block to the descrambling module at the AP side through the USB port; the EMM is sent to the CAS through the transmission of the broadcast channel or the interactive channel (FIG. 2 shows the transmission through the interactive channel), and then, the CAS calculates the CW according to the EMM and the ECM, and sends the CW to the descrambling module at the AP side through the USB port; the descrambling module uses the CW to descramble the scrambled media data block to obtain the clear stream, and sends the clear stream to the playing module, and then the playing module plays the clear stream. It can be seen that the media data block and the CW are separately sent to the AP side. Thus, after the scrambling is set at the AP side, although media contents transmitted through the USB port are scrambled, because the CW itself is easily monitored and intercepted, the security of keys is very low; correspondingly, the security of transmitted media contents is also low.
Furthermore, there are also problems similar to that above existing between other senders and receivers which have a transmitting and receiving relation and interact based on a non-secure transport protocol.
Aiming at the problem in relevant technologies that the data transmission based on the non-secure transport protocol cannot give consideration to both key security and content security, which causes transmitted contents to be easily stolen, no effective solution has been presented.